What is senescence and what role does it play in aging? We break it down for you below.
In this article:
- What Is Senescence?
- Why Does Cellular Senescence Occur?
- What’s the Link Between the Aging Process and Senescence?
Everything You Need to Know About Senescence (And Why It’s Such A Big Deal)
What Is Senescence?
Cellular senescence refers to a state where cells stop dividing. Cells in this state become unresponsive to growth stimulants and could be damaged. Senolytics is the process of destroying these senescent cells in order to reinvigorate new and healthy cell growth.
Leonard Hayflick first observed this cellular state in a fetal fibroblast which was metabolically active but was no longer dividing and multiplying. Senescent cells have the following biomarkers:
- Stable cell cycle arrest – These cells will not go through the cell cycle even when they interact with growth stimuli.
- Morphological and metabolic changes – They are usually larger and flatter compared to cells that are still undergoing cell division. They may have more vacuoles, multiple nuclei, and an increase in lysosomal content.
- Chromatin reorganization – They have reorganized genetic materials such as DNA and proteins.
- Altered gene expression – Certain proteins may be turned on or off which can alter the activity of the cell.
- Pro-inflammatory phenotype – They adopt a senescence-associated secretory phenotype (SASP) to mediate the non-cellular effects of cellular senescence. The SASP will communicate with other cells and the immune system in order to eliminate or proliferate tumor cell growth.
While cellular senescence may have evolutionary benefits, such as preventing the expansion of malignant (and potentially cancerous) or damaged cells, it may also contribute to aging and age-related pathologies. In fact, there is an increase in the number of senescent cells as you age. Aging is often tied closely with senescence for this reason.
Why Does Cellular Senescence Occur?
There are five main causes of cellular senescence:
- Telomere shortening
- DNA damage
- Oncogenic signaling
- Mitochondrial dysfunction
Telomere shortening is a result of replicative senescence which is a phenomenon where cells stop dividing after a certain limit (usually after approximately 50 divisions). This limit referred to as the Hayflick limit.
Every time DNA replicates, the telomeres get shorter and they eventually become too short to replicate further. When this happens, cell division stops which then leads to cellular senescence.
Cells respond to DNA damage in three ways: (1) cellular repair, (2) apoptosis (cell death), or (3) cellular senescence. The extent of the DNA damage will play a role in how the cells respond.
If the DNA damage is persistent, cellular senescence is more likely. For example, DNA damage caused by chemotherapy, genotoxic stress, ionizing radiation, and oxidative stress can also lead to senescence.
Oncogenic signaling is a pathway that could lead to the transformation of healthy cells into malignant cells. In these cases, cellular senescence may actually be one of the body’s natural anti-cancer mechanisms because it can stop these cells from proliferating.
What’s the Link Between the Aging Process and Senescence?
Biological aging and cellular senescence are not synonymous. However, you accumulate senescent cells as you age which makes it a likely contributor to aging and possibly even age-related diseases.
Researchers believe cellular senescence plays a role in the development of cancer, metabolic diseases, neurodegeneration, neurodegenerative diseases, and cardiovascular diseases. In fact, an animal study showed that you can reduce inflammation, improve the immune system, slow down age-related diseases, and improve overall health when you eliminate senescent cells.
There are also senolytic therapies which are a treatment that fights against senescent cells. This form of therapy has been found to increase the lifespan of mice.
Given these findings, scientists believe that limiting cellular senescence may have anti-aging effects. Minimizing the accumulation of cellular damage may prevent premature aging and help improve overall health.
There are things you can do to limit cellular senescence. There are also ways to increase cellular mitochondrial function to keep cells healthy and efficient, so contact an integrative health specialist today to learn about your options!
What do you think about the role of cellular senescence on aging? Let us know in the comments section.